BANDING ARTIFACT DETECTION IN DIGITAL VIDEO CONTENT

• US 20100066912A1
• Filed: 12/19/2007
• Published: 03/18/2010
• Est. Priority Date: 12/28/2006
• Status: Active Grant

• Current Assignee: InterDigital Madison Patent Holdings (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Dane, Gokce, Gomila, Cristina, Kumwilaisak, Wuttipong
• Granted Patent: US 8,532,198 B2
• Time in Patent Office: Days
• US Class Current: 348/607
• CPC Class Codes: G06T 7/44 using image operators, e.g. filters, edge density metrics or local histograms
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

A method and system for identifying and determining banding artifacts in digital video content composed of a sequence of moving video pictures includes creating a mask image corresponding to a picture from said sequence of moving video pictures based on global gradient changes to detect potential areas containing banding artifacts. The values of the mask image are scaled thereby making banding artifact detection possible using gradient operators. The banding artifacts are then identified/detected based on the local gradients.

Claims

1. A method of video processing digital video content comprising the steps:

generating a mask image based on global gradient changes of a video picture from said digital video content; and

detecting whether at least one area of said video picture has a banding artifact by using said mask image with a gradient operator as to determine a local gradient that indicates the presence of said banding artifact.

2. The method of claim 1, comprising the step of non-linearly scaling said mask image.

9. The method of claim 1, wherein said detecting step further comprises:

applying a pixel based gradient computation to the previously scaled data.

10. The method of claim 9, wherein said applying step is performed for both said reconstructed video information and said video picture when original digital video content corresponding to said video picture is available.

3. The method of 1, comprising the step of:

categorizing said at least one area of said video picture as having said banding artifact.

4. The method of claim 3, comprising the step of categorizing whether at least one area of said video picture is at least one of a smooth area, a slow change area, and a texture area.

11. The method of claim 3, further comprising the step of:

providing an indication as whether said at least one areas of a video picture from the digital video content has a banding artifact.

5. The method of 1, comprising the further steps of:

dividing said video picture into blocks having a pixel size;

computing an average pixel value for at least one block from said blocks forming a layer of the average pixel value for said at least one block;

computing the gradient of the formed layer; and

forming a binary large object in the layer having a determined size of a layer coefficient;

computing a value corresponding to said blob as to determine whether the area corresponding to said blob is at least one of a texture area, smooth area, and a slow change area by comparing said value to a threshold value.

6. The method of claim 5, wherein said value is a computed a mean and variance of the gradient of at least one layer coefficient of said blob;

and said method comprises the additional steps of;

comparing the mean and variance gradient value to said threshold value; and

performing at least one of the following steps;

marking said blob as a texture area when the mean and variance of the at least one layer coefficient of said blob are greater than said threshold; and

marking the blob as at least one of a smooth area and a slow change area when one of the mean and variance value of the at least one layer coefficient is less than said threshold.

7. The method of claim 6, comprising the additional steps of:

scaling non-linearly the mask image; and

applying pixel modification to at least one of processed video information and reconstructed video image representative of said video picture.

8. The method of claim 6, wherein said applying step additionally comprises:

determining if one or more blob areas are representative of a categorized image area of a size;

determining, for each of the one or more blobs, whether the blob area is marked as texture;

replacing all pixels in the blob areas with a constant value when marked as texture; and

scaling all pixels in the blob areas not marked as texture with a positive value.

12. A method of video processing comprising the steps:

generating a gradient field using an attribute associated a video picture from a sequence of video pictures;

creating a plurality of binary large objects (blobs) from elements from said gradient field, wherein a length and height of said plurality of blobs are larger than a length and height of associated with blocks of said video picture;

determining whether an area of said picture corresponding to a blob from said plurality of blobs is an area containing a banding artifact.

13. The method of claim 12, wherein said area of said picture corresponding to a blob from said plurality of blobs is identified as being at least one of a texture area, smooth change and a flat area.

14. The method of claim 12, wherein if said area is identified as being at least one of said smooth change or said flat area, performing a gradient masking operation on subject pixels associated with said area using an amplification factor.

15. A video encoder comprising:

a banding artifact detector having an input connected to an output of a reference picture buffer within the encoder, said detector configured to create a mask image of a video picture from a sequence of video pictures based on global gradient changes to detect potential areas containing banding artifacts, and scale values of the mask image to enable detection of banding artifacts.

16. The video encoder of claim 15, wherein said detector detects banding artifacts based on local gradients using gradient operators.

17. The video encoder of claim 16, wherein said detector further comprises a second input configured to be connected to the original video source, said detector utilizing said original video source as reference during detection of banding artifacts.

18. A program storage device having an application program tangibly embodied thereon, the application program including instructions for performing at least the following on a video picture from a sequence of video pictures:

using a mask image based on global gradient changes to detect an area of said video picture that contains a banding artifact; and

detecting banding artifacts based on local gradients using gradient operators.

19. The program storage device of claim 18, wherein the application program further includes instructions for performing at least the following:

categorizing said image area for determining whether said image area contains a banding artifact.

20. The program storage device of claim 18, wherein the application program further comprises instructions for performing at least the following:

dividing said video picture into blocks having a pixel size;

computing an average pixel value for at least one block from said blocks;

forming a layer of the average pixel value of the at least one block from said blocks;

computing the gradient of the formed layer;

forming at least one binary large object (blob) in the layer having a size of layer coefficient;

computing mean and variance of the gradient of the layer coefficients inside said at least one blob;

comparing the mean and variance gradient values to a threshold;

marking said at least one blob as a texture area when the mean and variance are both greater than said threshold; and

marking said at least one blob as at least one of a smooth area and a slow change area when one of the mean and variance values are less than said threshold.

21. The program storage device of claim 20, wherein the application program further comprises instructions for applying pixel modification to at least one of processed video information and reconstructed video picture representative of said video picture.

22. The program storage device of claim 20, wherein the application program further comprises instructions for:

determining if at least one blob is representative of a categorized picture area of a size;

determining, for each of the one or more blobs, whether the blob area is marked as texture;

replacing all pixels in the blob areas with a constant when marked as texture; and

scaling all pixels in the blob areas with a positive value when not marked as texture.

23. The program storage device of claim 20, wherein the application program further comprises instructions for performing at least the following:

applying a pixel based gradient computation to the previously scaled data.

24. The program storage device of 19, wherein the application program further comprises instructions for performing at least the following:

providing an indication to a user as to which area of said video picture has a banding artifact.